Preface

The crust is the hard, outermost layer of our planet, made up of different types of rocks. Although it is a thin layer, and is even less than 1% of the total volume of the Earth, it is very important because of its ability to sustain life. Dynamic geomorphic and geological forces have created the crust and tectonic activity is constantly playing its role in transforming the crustal materials that underlie the ocean basins and others that form the continents.

The rocks that form the crust are mostly composed of silicon, oxygen, calcium, aluminum, potassium, sodium, magnesium, and iron. These rocks are distinctive in their chemical composition and different from the underlining ultramafic upper mantle rocks. The crust is part of the lithosphere, which also includes the hard and brittle rock of the uppermost part of the upper mantle.

This book aims to cover the basics of the architecture, structure, evolution, and dynamics of the Earth's crust through an anthology of contributed chapters that will enlighten readers about the various aspects of the Earth's crust, including the existence, development, and sustainability of our modern lifestyles on its surface.

> **Dr. Muhammad Nawaz** National University of Singapore, Singapore

**1**

**Chapter 1**

*Muhammad Nawaz*

continued evolution to this day.

and (3) terrestrial model.

**2.1 Theories about the formation of the crust**

on the Earth's crust [2], making this theory highly unlikely.

**2. Origin**

**1. Introduction**

Introductory Chapter:

Earth Crust - Origin, Structure,

Earth crust is the thinnest and the most rudimentary layer that makes up the Earth, and yet, everything that has ever lived on Earth has called it home. The crust is a dynamic structure and it is one of the layers that make up our pale blue dot. The crust is referred to as a chemical layer that has varying chemical compositions. Two main types of crust are the oceanic crust and the continental crust, and they are different from each other. The differences are due to plate tectonics which then refers to plates and the movement of the plates above the asthenosphere, driving lithospheric processes that result in the formation and production of natural phenomena such as earthquakes and ridges. The crust is one of the five chemical layers of the Earth and is differentiated to show the distinct chemical properties occurring at each layer. The Earth's crust, along with the upper mantle, has its necessary role in the dynamic creation and destruction of the crustal surface in which all living organisms thrive on. This chapter will look at various aspects of the crust, and it will discuss the origin, structure and composition of the crust before elucidating its

The early terrestrial crust appeared approximately 4.5 billion years ago, after the late stages of planetary accretion. This section describes the theories of the formation of the crust and discusses the origin of the oceanic and continental crust.

There are three main theories on the formation of the Earth's crust [1]: (1) inhomogeneous or heterogeneous accretion of the Earth model, (2) impact model

The inhomogeneous model or the so-called the accretion model explains that the Earth's crust was formed during the accretion of the planet, with lighter and volatile elements forming a thin layer on the primitive planet which became the crust. This model suggests that non-volatile elements can only be found in the mantle; however, this is not true. Nonvolatile elements such as uranium and thorium are found

The impact model suggests that asteroids and other objects that impacted Earth

melted and formed the crust [1]. The oceanic crust, which is mainly composed

Composition and Evolution
